Install Instructions

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B. Ducting for Dehumidification (Example of typical ducting on page 7)
For the ideal installation, draw air from the central part of the home and return it to the isolated areas of the home like the
bedrooms, den, utility room, or family room. The duct work of the existing HVAC system can be used to supply air to the
home. If the existing supply duct adequately serves all areas of the home, discharge the supply air of the DH75 / DH100
into the return of the existing HVAC system where it can distributed throughout the space. The existing return duct, if
adequate, may be used as return for the DH75 / DH100. DO NOT draw air directly from the kitchen, laundry, bathroom,
or isolated basement. Air may be drawn from a basement that is open to the home. All exible ducting connected to the
DH75 / DH100 should be approved by local codes and in most cases insulated.
• Return air ducts should be designed to allow unimpeded air ow to the return side of the system. For returns less
than 10’ in length, an 8” round or equal may be utilized. Multiple returns are acceptable.
• The supply air outlet and the return air inlet are located on each end of the DH75 / DH100. A length of acoustical
ex ducting on the outlet of the DH75 / DH100 will reduce air noise. A length of exible ducting on all DH75 / DH100
duct connections is recommended to reduce noise and vibration transmitted to rigid duct work in the structure.
• Ducting the DH75 / DH100 as mentioned in the “Ducting” sections requires consideration of the following points:
• Duct Sizing: For total duct lengths up to 10’, use a minimum 8” diameter (DH75) and 10" (DH100) round or
equivalent rectangular. For longer lengths, up to 25’, use a minimum 10” diameter or equivalent duct size. Grills
or diffusers utilized must not excessively restrict airow.
• Isolated Areas: Effective dehumidication may require that ducting be branched to isolated, stagnant
areas. Use 8” or larger diameter branch ducting to each of two or three areas, use 6” or larger to each of
four or more areas.
• Connecting to Existing HVAC Systems: For proper operation, connecting to existing air handler and duct
systems requires the fans of each system to be interlocked using the low voltage interlock method provided in
the DH75 / DH100 low voltage connection diagram. Refer to low voltage connection diagram in this document
and on the unit.
C. Installation in Basement or Crawl Space with Existing Forced-Air HVAC System (WH)
If the structure in which the DH75 / DH100 system is to be installed has an existing forced-air HVAC system, and this
system serves the areas that are desired to be controlled, use the HVAC system to make the DH75 / DH100 installation
easier and provide better whole house type system performance.
Basement or Crawl Space Installation: Install a separate 8” return for the DH75 / DH100 in a central area of the
structure or if the return ducting is adequate tap into the existing return duct system near the return air grill. Duct the
supply of the DH75 / DH100 System to the return ducting of the existing HVAC system. The fan interlock provision must
be utilized for proper system performance.
D. Installation in Attic with an Existing Forced-Air HVAC System (WH)
IMPORTANT: A secondary drain pan MUST be installed with a drain or oat interrupt for condensation under the DH75
/ DH100 in an attic to prevent condensate overow that may drip down, damaging the ceiling or living space below.
Install a separate 8” return for the DH75 / DH100 in a central area of the structure or if the return ducting is adequate tap
into the existing return duct system near the return air grill. Duct the supply of the DH75 / DH100 System to the return
ducting of the existing HVAC system. The fan interlock provision must be utilized for proper system performance.
E. Installation in Structure with Two Forced-Air HVAC Systems (WH)
Attach the DH75 / DH100 return to an independent return from the upper level. Attach the DH75 / DH100 supply to the
return of the basement HVAC system. This will promote circulation of air through the whole structure from the upper level
to the lower level through the DH75 / DH100. If the DH75 / DH100 is not connected to both HVAC systems, it may not
control the humidity of the entire structure. The fan interlock provision should be connected to the lower ducted HVAC
system and must be utilized for proper system performance.
• WH = Whole House Dehumidification
• SP = Spot Dehumidification
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